Análise de marcas de predação em cetáceos utilizando foto-identificação

Abstract

In Brazil, despite the increase in research and conservation efforts in the last two decades, it is still incipient studies related to cetaceans, and has few informations referring to their oceanic habits. Much of the knowledge about this group was obtained from information coming from commercial resources, captivity or animals accidentally caught or found dead. Sharks are important predators, and have some preference for pinípedes and small cetaceans, but also large cetaceans may be part of the diet of certain species of shark. The analysis of lesions caused by whales is easily accomplished through images, since the skin of these animals is in many cases dark, due to the healing process that occurs without the presence of melanocytes, resulting whitish scars. Thus, this study aimed to analyze predation marks on cetaceans through photo-identification, to identify the species involved and record the occurrence of such attacks through a stock photography images. Were analyzed a total of 1482 photographs, recorded between 2002 and 2010 along the coast of the Litoral Norte, Costa de Itacaré and Banco de Abrolhos. The images were first separated into quality categories (A), (B), (C) and (D) where in "(A) Excellent – It has all the quality criteria", "(B) Good - Some of the criteria quality has been compromised ", "(C) Average - Two or more quality criteria were committed and "(D) Poor - One or more quality criteria were committed enough to make not identify", then the images has been selected for the categories (A) and (B) for analysis. These were classified into (0) and (1), where "(0) No bite presence" and "(1) Bite presence" identifying then the lower possible taxonomic level of the animals involved. In all, five species of cetaceans were identified containing predation marks, these at least 13 different individuals of Humpback whale (Megaptera novaeangliae), 2 Common Minke whale (Balaenoptera acutorostrata) , 2 Risso's dolphin (Grampus griseus), 1 Rough-toothed dolphin (Steno bredenensis) and 1 Guiana dolphin (Sotalia guianensis). 100% of the analyzed images containing predation marks was possible to see at least one scar from predation by Cookie Cutter shark. In only one case was noted predation mark from another predator, probably caused by White Shark or Tiger Shark, due to the size of the bite. A Jubarte carcass was also sighted being preyed by Tiger shark.